Buggy code:
public class typeChecker implements Visitor < Object , Type > { private ErrorReporter reporter ; private int numMainFunc ; MethodDecl mainMethodDecl ; MethodDecl printlnDecl ; MethodDecl printlnStringDecl ; private void checkForMain ( MethodDecl md , Type retType ) { } private typeEquality isEqual ( Type el , Type er ) { } private Type getTypeOfExpr ( Type t , Operator o ) { } private Type getTypeOfExpr ( Type l , Type r , Operator o ) { } Type operatorAgreement ( Type l , Type r , Operator o ) { } private Type typeCheckAssignment ( Type l , Type r ) { } public typeChecker ( ErrorReporter er , MethodDecl _printlnDecl , MethodDecl _printlnStringDecl ) { } class TypeCheckError extends Error { private static final long serialVersionUID = 1L ; } private void typeCheckError ( String e ) { } private void typeCheckFatalError ( String e ) throws typeChecker . TypeCheckError { } public MethodDecl typeCheckAST ( AST ast ) { } public Type visitPackage ( AbstractSyntaxTrees . Package prog , Object arg ) { } public Type visitClassDecl ( ClassDecl clas , Object arg ) { } public Type visitFieldDecl ( FieldDecl f , Object arg ) { } public Type visitMethodDecl ( MethodDecl m , Object arg ) { } public Type visitParameterDecl ( ParameterDecl pd , Object arg ) { } public Type visitVarDecl ( VarDecl vd , Object arg ) { } public Type visitNullDecl ( NullDecl decl , Object arg ) { } public Type visitBaseType ( BaseType type , Object arg ) { } public Type visitClassType ( ClassType type , Object arg ) { } public Type visitArrayType ( ArrayType type , Object arg ) { } public Type visitBlockStmt ( BlockStmt stmt , Object arg ) { } public Type visitVardeclStmt ( VarDeclStmt stmt , Object arg ) { } public Type visitAssignStmt ( AssignStmt stmt , Object arg ) { } public Type visitIxAssignStmt ( IxAssignStmt stmt , Object arg ) { } public Type visitCallStmt ( CallStmt stmt , Object arg ) { } public Type visitReturnStmt ( ReturnStmt stmt , Object arg ) { } public Type visitIfStmt ( IfStmt stmt , Object arg ) { } public Type visitWhileStmt ( WhileStmt stmt , Object arg ) { } public Type visitForStmt ( ForStmt stmt , Object arg ) { } public Type visitUnaryExpr ( UnaryExpr expr , Object arg ) { } public Type visitBinaryExpr ( BinaryExpr expr , Object arg ) { } public Type visitRefExpr ( RefExpr expr , Object arg ) { } public Type visitCallExpr ( CallExpr expr , Object arg ) { } public Type visitLiteralExpr ( LiteralExpr expr , Object arg ) { } public Type visitNewArrayExpr ( NewArrayExpr expr , Object arg ) { } public Type visitNewObjectExpr ( NewObjectExpr expr , Object arg ) { } public Type visitQualifiedRef ( QualifiedRef qr , Object arg ) { } public Type visitIndexedRef ( IndexedRef ir , Object arg ) { } public Type visitIdRef ( IdRef ref , Object arg ) { } public Type visitThisRef ( ThisRef ref , Object arg ) { } public Type visitNullRef ( NullRef ref , Object arg ) { } public Type visitIdentifier ( Identifier id , Object arg ) { Type idType = id . getDecl ( ) . type ; if ( ( idType . typeKind ) == ( TypeKind . UNSUPPORTED ) ) typeCheckFatalError ( ( ( ( "Encountered<seq2seq4repair_space>UNSUPPORTED<seq2seq4repair_space>type<seq2seq4repair_space>for<seq2seq4repair_space>" + id ) + "<seq2seq4repair_space>of<seq2seq4repair_space>name<seq2seq4repair_space>" ) + ( id . spelling ) ) ) ; <START_BUG> return id . getDecl ( ) . type ; <END_BUG> } public Type visitOperator ( Operator op , Object arg ) { } public Type visitIntLiteral ( IntLiteral num , Object arg ) { } public Type visitBooleanLiteral ( BooleanLiteral bool , Object arg ) { } public Type visitStringLiteral ( StringLiteral s , Object arg ) { } }

Fix:
return idType ;